What’s in a name...? This form attempts to find and load all of the referenced
system files starting with any systems in systems. It does not include the systems
themselves unless they are syb-systems of some other system in the list.

Returns true if, metaphorically speaking, system-name is a system unto itself. Usually, this means that there are no systems that depends on the system but it could also be that the system is used by other systems but is also coherent in and of itself.

5.1.2 Generic functions

Applies function to each of the files named in system-name/s. If system-closure? is true, then function is applied to the files of the systems that this system depends on. If incude-pathname? is true, the the function is applied to complete pathnames; otherwise the function is applied only to the name+type of each file. If include-non-source? is true, then all files are included. If it is nil (the default), then only source files will be included.

Returns true if, metaphorically speaking, system-name is a system unto itself. Usually, this means that there are no systems that depends on the system but it could also be that the system is used by other systems but is also coherent in and of itself.